The present invention relates to the ecological method of phyto-remediation of alkaline and chemically degraded soils using scented geranium (Pelargonium sp.).
The world arable land resources are finited 78% of earth surface is unusable for agriculture and the 22% usable one includes only 3% of the earth surface as high productivity soils for intensive crop production whilst 6% and 13% are the values for the medium and low capacity soils, respectively. Thus, a substantial part of the agriculturally usable soil requires restoration and improvement on a continuous basis. Soil alkalinity (natural or agriculturally and industrially imparted) is one of the major causes of the poor productivity and chemical degradation of the soils on a global basis, Chemical methods of reclamation of the alkaline soils include application of soluble calcium salts like gypsum and phosphogypsum, use of sparingly soluble calcium salts like Calcite and amendments with acids or acid formers like H2SO4, iron and calcium sulfates, lime sulfur and pyrite etc.
However, the organic methods of soil reclamation are ecologically more acceptable and sustainable. There are several reports in the prior art on vegetation with specific plant species like rice (R. K. Gupta, R. R. Singh and I. P. Abrol, 1988, Soil Sci. 146:395), Prosopis juliflaura (R. K. Saxena, K. S. Veram, R. C. Sharma, R. Srivastava and A. K. Barthwal, 2000. International Conference on managing Natural Resource for sustainable Agriculture Production in the 21ST Century, New Delhi February 14-18, 2000, Extended Summaries Vol. 2, pp. 14-16) for improvement of soil properties.. In general, some reduction in alkalinity due to organic residues is owing to growth of microbes on the available organic matter (and attendant liberation of carbon dioxide). This effect is secondary in nature and has no specificity of organic matter as anything from plant residues to sludge and sewage waste can function as substrate (T. J. Logan, 1992, Advances in Soil Sci. 17: 13-31 and references their in). Being, dependent on the microbial growth etc. its impact is obviously slight in magnitude and temporarily delayed. Thus, although there are several attempts in the prior art to reduce alkalinity in the soil, there is no report on the use of weeds or spent biomass for reclamation of alkaline soil.
It is the applicant""s finding that the scented geranium biomass is useful in reclamation of alkaline soil by two mechanisms, first being direct (immediate) neuralization with very high acid content of the biomass (i.e as an accident), and second being usual (slight and delayed) biomass degradation associated phenomenon of pH neutralization.
This method provides an ecological alternative to the employment of chemical method of acid aided neutralisation of alkaline soil.
Further, scented geranium is a modern cash crop of robust growth cultivated for valuable exotic essential oil obtained from hydrodistillation of its aerial biomass, The essential oil possesses a delicate fragrance which is widely used in perfumery, cosmetic and flavour industries and aromatherapy (E. Gildemeister and Fr. Hoffmann, 1959, Die atherischen Ole. Vol. 5,p. 350, Akademie-Verlag, Berlin). The distillation-residual water as well as the distillation-residual biomass considered as wastes are strongly acidic in nature and can be employed to rejuvenate various sorts of alkaline soils. Thus, in addition to economic returns in the form of essential oil from harvestable biomass, the distillation-residual aerial biomass serves as an ideal material for employment in the reclamation of soils with alkalinity problem at farmers level (cottage practice) as well as at the commercial level of marketing. The approach besides being ecologically acceptable is a sustainable way of staling the patterns of development of alkalinity in the soils as a consequence of modern cropping and crop management practices and certain micro-environmental factors.
The main object of the present invention is to provide an ecological method of phyto-remediation of alkaline and chemically degraded soils using scented geranium (Pelargonium sp.).
Another object is to provide a novel method for reclamation of alkaline soil using biomass of scented geranium.
Accordingly, the invention provides a novel method for reclamation of alkaline and contaminated soil by the use of scented geranium biomass, which may be fresh or obtained after distillation process.
The present invention provides a novel ecological method of phyto-remediation of alkaline and chemically degraded soils, said method comprising the steps of:
(a) dispersing fresh geranium biomass in alkaline or chemically degraded soil in ratio of 1:0.01 to 0.075, or
(b) applying distillation residual water to the soil of step (a) in the ratio of 6:1-8:1, preferably 7.5:1.
In an embodiment, the scented geranium comprises plant of Pelargonium species.
In another embodiment fresh aerial biomass obtained after distillation of essential oil from the plant is used.
In still another embodiment, geranium biomass is mixed or dispersed with the alkaline or chemically degraded soil.
In yet another embodiment the pH of the alkaline soil is  greater than 8.5.
In another embodiment, the residual water obtained after distillation of essential oil from the biomass is percolated in the alkaline or chemically degraded soil.
In another embodiment, the treatment is continued for 4 weeks.
In an embodiment of the present invention fresh or distillation-residual aerial biomass of scented geranium (Pelargonium sp.) may be used for phyto-remediation of alkaline and contaminated soils.
In another embodiment of the present invention distillation-residual water of scented geranium may be used for the reclamation of alkaline soils.
The present invention provides an ecological method of phyto-remediation of alkaline and chemically degraded soils using scented geranium (Pelargonium species) which comprises treatment of the alkaline soil (pH greater than 8.5) by dispersion or mixing of fresh aerial biomass or distillation-residual aerial biomass (obtained from essential oil distillation unit) or percolation of the distillation-residual water from scented geranium distillation unit. In case fresh Pelargonium aerial biomass is used, the soil to biomass ratio is in the range of 1:0.01 to 0.075 (w/w: soil:fresh aerial biomass). If dry distillation-residual aerial biomass is used, this treatment is followed by intermittent moistening of the mix for up to four weeks (or more). In case dry distillation residual aerial biomass is used, this biomass is mixed with the soil. The soil:biomass ratio being 1:03 to 0.06 w/w. If distillation-residual water from scented geranium distillation unit is used, then the ratio of soil: to distillation-residual water is 6:1 to 8:1, preferably 7.5:1. Such treatment of alkaline and chemically degraded soil with Pelargonium sp. resulted in the fall in pH of the alkaline soil.
The applicants have found that aerial plant parts of scented geranium are highly acidic in nature with cell sap pH of about 3.0 especially in parts like leaf lamina and floral parts (sepals and petals). Acidity of two volume aqueous extract of these fresh tissues was found to be more than S milliequivalents of sodium hydroxide. Since the aerial part of the plant yields acidic extract, these extracts are capable of bringing down the pH of alkaline or chemically degraded soil. It is for this reason that the applicant has used this plant in the phyto-remediation method for the soil alkalinity. pH of the distillation-residual water was found highly acidic (pH 3.5) when checked after distilling 200g of scented geranium aerial biomass in 200 ml of distilled water.
Thus, this invention provides an ecological approach of phyto-remediation of alkaline and contaminated soils through fresh and distillation-residual aerial biomass of scented geranium (Pelargonium sp.). The method of this invention can be adopted to rejuvenate the alkaline and chemically degraded soils including naturally alkaline soils, agricultural system associated alkalizing soils, mining rejected alkaline wastes (like Red Mud produced from bauxite) imparted alkaline soils, mine reject soils with acidic reaction and low organic carbon etc. The usage of this method, besides its usual role in imparting degradable organic matter stimulates biolic activities and improves physical properties of the soil.
The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the present invention.